OF THE CENTRAL MOTOR INNERVATION OP THE LARYNX. 
207 
excitation of the restiform body in a vertical direction beginning below, opposite and 
close to the upper end of the region just referred to as giving bilateral adduction, and 
proceeding along the outer part of the floor of the fourth ventricle as high as the 
centre of that cavity. (See fig. 9.) 
Whether the adduction of the vocal cord of the same side obtained by excitation 
in the line thus drawn is due to excitation of the nucleus reserved for the movements 
of the vocal cord of the same side, or whether it is rather excitation of those fibres 
which run through the substance of the medulla, to appear at oirce as the roots of the 
vago-accessory nerves, remains doubtful, though we are naturally more inclined 
towards the latter view. However, we do not consider that any positive opinion can 
at present be expressed upon this point. 
Abduction .—It has been mentioned above that the movement of abduction is 
obtained over the situation of the upper two-thirds of the ala cinerea and also from 
about the origin of the eighth nerve. This latter area is evidently more important 
and extends upwards to close to the debouchment of the aqueduct of Sylvius. (See 
fig. 9.) Further, this movement of abduction is persistent, and is better marked a short 
distance, about 2 mm. from the middle line, than in the middle line itself. We have 
never observed unilateral abduction similar to the unilateral adduction before 
mentioned. 
It may be that fibres exist in f he tegmentum or crusta which directly connect together 
the cortical and bulbar mechanisms now described, and that, as before suggested, the 
observations which would point to respiratory mechanisms existing in the basal parts 
of the cerel3ral hemisphere and in the mesencephalon have Ijeen the results of stimula¬ 
tion of such fibres by those looking for respiratory centres in these positions. 
Before we had recognised completely the degree to which the etherisatioii must be 
carried v/e obtained some results upon the larynx when the dorsal surface of tlie 
spinal cord, i.e., below the calamus sciiptorius, was stimulated, but we saw from the 
first that the results obtained here were probably those of a reflex nature, and further 
investigation has confirmed this opinion. For tire effects were only jiroduced in their 
entirety as the excitation approaclied successively the posterior roots, and diminished 
as the electrodes were moved to intermediate parts of the spinal cord. Further, the 
effects were far more in the nature of acceleration of thoracic respiration than primary 
changes in the movements of tlie larynx. 
We never observed any after effects, e.r/., clonus, &c., upon cessation of the stimula¬ 
tion of the medulla oblongata. 
Injilienee of Age. 
Those acquainted with the historv of previous research on the subject of the 
innervation of the larynx know well that, from the first, experimental investigation 
has shown that there exists, according to the age, a great difference in the same 
